1. Field of the Invention
The present invention relates to a machine for stabilizing a track comprised of rails fastened to ties and extending in a longitudinal direction, which comprises a machine frame supported on the track by undercarriages for mobility along the track, and two track stabilization units linked to the machine frame by vertical adjustment drives, the track stabilization units being spaced from each other in the longitudinal direction and running on the track. Each track stabilization unit comprises a generator of oscillations connected to a drive for producing oscillations extending perpendicularly to the longitudinal direction.
2. Description of the Prior Art
The structure and operation of such a machine, commonly known as a dynamic track stabilizer, has been described in an article entitled "Erfahrungen und Ergebnisse aus dem Einsatz des dynamschien Gleisstabilsators" (Experiences and Results of the Use of the Dynamic Track Stabilizer), in the periodical "Eisenbahntechnische Rundschau" (Railroad Technical Review), October 1987, pp. 663-667. Two track stabilization units are mounted on a machine frame between the undercarriages on which the machine frame is supported for mobility on the track and a total of eight flanged wheels, and freely rotatable rollers gripping the rail heads at the field sides of the rails tightly hold the track rails connected to the track stabilization units. While the machine continuously advances along the track, the two synchronized oscillation generators impart horizontal, unidirectional oscillations to the track, which extend perpendicularly to the longitudinal direction of the track. The frequency of the oscillations varies from 0 to 45 Hz and, depending on the frequency, the force of impact varies from 0 to 350 kN.
At the same time, four hydraulic vertical adjustment drives, which link the track stabilization units to the machine frame, subject the track to a vertical load. The maximum vertical load is 360 kN. The horizontal oscillations and the simultaneous vertical load exerted by the track stabilization units causes the ballast in the cribs and under the ties to be compacted. This ballast compaction not only settles the track in the ballast but has the additional essential effect of increasing the friction between the ties and the greatly compacted ballast bed so that the resistance of the track to lateral displacement is maximized. A hydrostatic drive connected to the oscillation generators steplessly controls the generators to adapt the dynamic ballast compaction to the prevailing ballast bed conditions.
Numerous tests have shown that the vibrations caused by the oscillating track have no damaging impact on structures which are close to the track but they sometimes arouse anxiety or other negative feelings among passers-by and others who are not familiar with this track operation, particularly in densely populated areas.
By way of example, dynamic track stabilizers have been disclosed also in U.S. Pat. Nos. 4,046,078, 4,046,079 and 4,064,807.